Pulleys are used for a variety of purposes. For example, a pulley may be installed on a motor to drive a fan pulley to produce air by connecting a belt between both pulleys. For a motor pulley to drive a fan pulley efficiently, the centerline of both pulleys must be aligned. Otherwise, the belt may twist and fail prematurely. A pulley may have either a fixed or variable sheave. The fixed sheave pulley has one operating position while a variable sheave pulley can be set to operate at various positions. Pulleys may become misaligned for a number of reasons including when a pulley is replaced, a belt is changed, or the operating position of a variable sheave pulley is changed.
The most common method of aligning pulleys involves holding a straight edge against the outer surface of the sheaves of both pulleys. When the straight edge is rested against the outer surface of the sheaves of the pulleys, the pulleys are said to be aligned. Obviously, this method of alignment is dependent on the interpreter. This method also does not work to align a variable sheave pulley when its operating position is changed.
Another method of aligning pulleys involves using a straight line laser light pointer and targets. With this method, the straight line laser light pointer is attached to a sheave of the motor pulley and the targets are attached to a sheave of the fan pulley. The pulleys are aligned when the laser light from the pointer falls on marks on the targets simultaneously. Although the laser method offers a more accurate method of aligning pulleys with fixed sheaves than the straight edge method, the laser method also does not accurately align a variable sheave pulley when its operating position is changed.